U.S. patent number 4,237,980 [Application Number 06/020,819] was granted by the patent office on 1980-12-09 for check valve for fluid-producing wells.
This patent grant is currently assigned to R & C Machine Devon Ltd.. Invention is credited to Robert G. Robinson.
United States Patent |
4,237,980 |
Robinson |
December 9, 1980 |
Check valve for fluid-producing wells
Abstract
A check valve is provided for use in the tubing string of a
fluid producing well. The check valve is removably seated within
the restricted diameter of a seating nipple in the tubing string.
Resilient holddown means at the base of the valve are provided for
this purpose. The check valve comprises a hollow generally tubular
body having a pierceable valve element positioned therein, the
valve opens and closes in response to fluid pressures bearing
thereon. To equalize the pressures above and below the valve the
pierceable valve element may be ruptured by a conventional wireline
spear, allowing the fluid to drain slowly through the valve.
Inventors: |
Robinson; Robert G. (Edmonton,
CA) |
Assignee: |
R & C Machine Devon Ltd.
(Edmonton, CA)
|
Family
ID: |
21800771 |
Appl.
No.: |
06/020,819 |
Filed: |
March 15, 1979 |
Current U.S.
Class: |
166/317;
137/533.21; 166/322; 166/324; 166/325 |
Current CPC
Class: |
E21B
34/06 (20130101); E21B 34/063 (20130101); Y10T
137/7915 (20150401) |
Current International
Class: |
E21B
34/00 (20060101); E21B 34/06 (20060101); E21B
034/08 () |
Field of
Search: |
;166/317,322,324,325
;135/533.21,68 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Pate, III; William F.
Attorney, Agent or Firm: Wymore; Max L.
Claims
The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. A check valve for controlling back flow in the tubing string of
a fluid-producing well, said string having a submersible pump
positioned at its lower end, said tubing string further
incorporating a seating nipple above the submersible pump, said
check valve comprising:
a retrievable generally tubular body adapted to seat in the seating
nipple and having a first longitudinal bore extending therethrough,
said body forming an annular valve seat and a stop shoulder spaced
above the valve seat, said valve seat and stop shoulder defining
the ends of a chamber which is part of the bore;
a generally tubular valve element having a second longitudinal bore
and being disposed in the chamber, said valve member having a
transversely extending wall which is pierceable by a wireline tool
and which closes off the second bore against fluid flow
therethrough, said valve element being operative to prevent fluid
flow through the first bore when it seats on the valve seat, said
valve element being operative to permit fluid flow through the
first bore when the valve element is unseated, the cross-sectional
area of the peirceable wall available to be pierced being
substantially less than the cross-sectional area of the first bore,
whereby, when the wall is pierced, only restricted flow is
permitted therethrough so as to avoid damaging the submersible
pump.
2. The check valve as set forth in claim 1 wherein:
the first bore is of reduced cross-section at its upper end and
expanded cross-section throughout the chamber length;
the tubular body has one or more ports extending through the
chamber wall above the valve seat;
said valve element comprises an upper tubular shaft and lower
outwardly flared tubular head portion, said shaft sliding in the
reduced cross-section of the first bore, said head portion sliding
in the expanded cross-section of the chamber;
said pierceable wall extending across the second bore at the
junction of the shaft and head portion; and
said head portion being inwardly spaced from the wall of the
tubular body to define a clearance for fluid flow past said head
portion.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a check valve for use in a fluid
producing well. More particularly the invention relates to a
retrievable check valve which provides simple means for
equalization of pressures above and below the valve.
Check valves are commonly used within a string of tubing of a fluid
producing well wherein a submersible pump is being used to move
fluid to the surface. The pump is usually located at the fluid
bearing formation, adjacent the foot of the string of tubing.
Usually impellors within the pump are electrically driven to force
the fluid upwardly. Thus, while the pump is in operation, a column
of fluid extends the length of the tubing string above the pump. In
the event of stopping the pump, this suspended column, if not
restricted, would back flow through the pump. This back flow would
reverse the impellors at high speed, thereby causing damage to the
thrust bearings. Therefore a check valve is placed in the tubing
string above the pump to regulate the back flow of fluid through
the pump.
Many such check valves are in common use, the simplest of which is
a ball-in-a-cage valve. Here a tubular cage is provided having a
seat at its lower end. A ball within the cage seats on the seat and
is dislodged in response to the upward flow of fluids. Back flow
however is restricted as the ball becomes reseated. Such valves
suffer the disadvantage known as "squirrel caging", wherein the
gaseous nature of the fluid flow causes the ball to bounce around
in the cage, causing damage to both the ball and cage, and
ultimately resulting in a loss of effective seal.
Flapper check valves are also known in the art. According to this
design, a horizontal flap in a tubular body is hinged to open and
close in response to flow pressures bearing from above and below
the valve. In the past, both the flapper and the ball-in-a-cage
type valves have had the tubular body threaded into the tubing
string, making the valves non-retrievable by design. Thus to
replace or repair the valve, it was necessary to pull out the
entire tubing string, a time-consuming and costly process.
A further type of check valve used in well strings is the dart-type
valve. A dart is seated in the lower portion of a closed tubular
body and is provided with an upper tubular shaft. A narrow upper
neck portion of the tubular body guides the dart shaft as the dart
is translated upwardly to allow flow past the valve. Valves of this
type are generally subject to jamming problems, since considerable
sand tends to lodge itself in the upper tubular body above the dart
shaft, restricting the upward movement of the dart.
These previously described check valves commonly suffer the
disadvantage of not providing simple means to equalize pressures
above and below the valve. Once the valve has closed to restrict
back flow of the fluid therethrough, it is desirable to allow the
column of fluid suspended above the valve to drain slowly past the
valve to thereby equalize pressures without damaging the thrust
bearings. Otherwise, to remove the valve or pump, the tubing
string, laden with the fluid column, must be pulled to the surface.
In deep wells, the additional weight of the fluid column is
considerable, making the pulling operation difficult.
Heretofore, to provide for equalization in check valves has been a
complicated matter of providing by-pass ducts which open and close
either by surface control or in response to changing pressures
bearing on the valve. For instance, in U.S. Pat. No. 2,994,280 to
Daffin, there is disclosed a retrievable check valve of a
ball-in-a-cage design which is provided with equalization means.
Shear pins are used to hold an outer sleeve of the tubular body in
place. An upward pull on the valve shears the pins, allowing the
sleeve to translate upwardly, thereby aligning bypass ports of the
sleeve and inner tubular body to allow fluid to flow
therethrough.
SUMMARY OF THE PRESENT INVENTION
The present invention provides a check valve which seats in a
seating nipple position above a submersible pump in the tubing
string of a producing well.
The check valve is designed to be retrievable. It comprises a
hollow, generally tubular body having conventional latching means
at its upper end for engaging a wireline tool inserted in the
string to remove it. The tubular body further comprises
conventional resilient holddown means at its lower end, for
anchoring the valve in the seating nipple, and conventional
shoulder means between its ends, for preventing downward
displacement of the body through the seating nipple.
The tubular body is flow through in design, having a longitudinal
bore extending therethrough. The bore is preferably reduced in
cross-section at its upper end and the body thus forms an inwardly
projecting stop shoulder for a purpose to be explained. Spaced
below this stop shoulder, the tubular body wall projects inwardly
to form an annular valve seat. The portion of the body bore between
the seat and the stop shoulder is termed the valve chamber.
A valve element is positioned within the valve chamber. The valve
element is vertically moveable within the chamber. When seated by
downwardly directed pressure onto the annular valve seat, the valve
element prevents downward fluid flow through the bore. When
unseated by pressure from below, a clearance between the outer rim
of the valve body and the inner surface of the valve chamber wall
permits upward flow around the valve element. The stop shoulder
limits upward travel of the valve element.
The valve element comprises a generally tubular body having a
transversely extending pierceable wall closing off or sealing its
longitudinal bore. The cross-sectional area of that segment of the
pierceable portion which is exposed or available to be pierced is
substantially less than any cross-sectional area of the
longitudinal bore of the tubular body. Thus, when the pierceable
portion is pierced (as by a wireline spear), the drain opening so
formed is relatively small and back flow through it is restricted,
whereby the submersible pump is not damaged by such back flow.
Broadly stated, the invention is a check valve for controlling back
flow in the tubing string of a fluid-producing well, said string
have a submersible pump positioned at its lower end, said tubing
string further incorporating a seating nipple above the submersible
pump, said check valve comprising: a retrievable generally tubular
body adapted to seat in the seating nipple and having a first
longitudinal bore extending therethrough, said body forming an
annular valve seat and a stop shoulder spaced above the valve seat,
said valve seat and stop shoulder defining the ends of a chamber
which is part of the bore; a generally tubular valve element having
a second longitudinal bore and being disposed in the chamber, said
valve member having a transversely extending wall which is
pierceable by a wireline tool and which closes off the second bore
against fluid flow therethrough, said valve element being operative
to prevent fluid flow through the first bore when it seats on the
valve seat, said valve element being operative to permit fluid flow
through the first bore when the valve element is unseated, the
cross-sectional area of the pierceable wall available to be pierced
being substantially less than the cross-sectional area of the first
bore, whereby, when the wall is pierced, only restricted flow is
permitted therethrough so as to avoid damaging the submersible
pump.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional side view, illustrating the check valve
seated within the tubing string of a fluid producing well.
FIG. 2 is a perspective view of the check valve having a cut-away
portion to illustrate the valve element in cross-section.
FIG. 3 is a perspective view of the valve element having a cut-away
portion to illustrate the pierceable disc.
DESCRIPTION OF THE PREFERRED EMBODIMENT
With reference to the drawings, the check valve of the present
invention is comprised of hollow generally tubular body 1 having a
pierceable valve element 2 positioned therein. Restrictive element
2 is free to open and close in response to pressures bearing on it
from below and above.
The tubular body 1 is shown in FIG. 1 removeably seated in a
conventional seating nipple 3 threaded into the tubing string 4.
The seating nipple 3 is located one or more lengths of tubing above
an electrical submersible pump 5. Leaving this amount of space
between the check valve and the pump is desirable to limit large
gas pockets from forming therebetween when the pump is stopped.
Large gas pockets cause considerable problems in restarting the
pumping operation.
Seating nipples are conventionally used in seating well tools
within tubing strings by providing regions having smaller internal
diameter than that of the tubing. Seating nipple 3 is threaded at
its upper and lower ends 6 and 7 respectively, to be secured into
the tubing string 4. The upper edge of the seating nipple provides
an upper landing seat 8, on which is seated tubular body 1. The
lower edge of the seating nipple provides a holddown shoulder 9 to
restrict the upward displacement of the tubular body 1 under the
normal upwardly directed pressures of fluids being pumped to the
surface.
THE TUBULAR BODY
The hollow, generally tubular body 1, as seen in FIG. 2, comprises
an upper body portion 11 and a lower body portion 12. A first
longitudinal bore 36 extends through the body 1. The lower body
portion 12 is threadably received by the upper body portion 11. An
outwardly protruding lip 14 is provided at the upper end of the
lower body portion 12. In order to seal the body portions 11 and 12
together, a packing ring 13 is carried by the lip 14 between the
body portions 11 and 12.
The lower body portion 12 has an external diameter substantially
equal to the internal diameter of the seating nipple 3 for close
fitting relationship thereinto. The packing ring 13 has an external
diameter slightly larger than the external diameter of the lower
body portion. In this way, when the lower body portion 12 is fitted
in seating nipple 3, the packing ring 13 bears on the inner wall of
the seating nipple 3 to seal against leakage around the valve.
In order to removeably seat the tubular body in the seating nipple
3, resilient holddown means 15 are provided at the lower end of
lower body portion 12. To form the resilient holddown means 15, the
lower body portion 12 is flared outwardly at 16 to form a holddown
collar 17. This collar 17 thus has an external diameter greater
than the internal diameter of the seating nipple 3. The holddown
collar 17 is tapered inwardly at 18 to facilitate the installation
of the tubular body 1 into the seating nipple 3. The lower body
portion 12 has at its lower end circumferentially spaced cut-out
portions 19 extending a substantial distance upwardly past the
holddown collar 17, to form a plurality of resilient flanges 20.
The flanges 20 can be squeezed inwardly to allow the holddown
collar 17 to be passed through the narrow internal diameter of the
seating nipple. Once clear of the seating nipple however, the
flanges 20 spring back to their original shape to restrict the
upward displacement of the tubular body 1.
Downward displacement of the tubular body 1 past the seating nipple
3 is limited by the construction of the upper body portion 11. The
upper body portion 11 has a widened intermediate portion 21 of
external diameter greater than the internal diameter of the seating
nipple 3 but not greater than the internal diameter of the tubing
string 4. This intermediate portion 21 is tapered inwardly at 22 to
form an upper landing shoulder 23. When the tubular body 1 is
positioned in the seating nipple 3, this upper landing shoulder 23
seats on the upper landing seat 8 of the seating nipple 3. It will
now be noted that the distance between the upper landing shoulder
23 and the holddown collar 17 of the tubular body 1 must be
substantially equal to the distance between the upper landing seat
8 and the holddown shoulder 6 of the seating nipple 3, to allow a
fitting relationship.
The upper end of the upper body portion 11 is tapered inwardly at
24 to provide a narrow latching neck portion 25. This latching neck
25 can be engaged by a wireline tool (not shown) to remove the
tubular body 1 from the seating nipple 3. For this purpose, the
uppermost end of the latching neck is beveled to form a latching
head 26.
The valve element 2 is positioned in the upper body portion 11 of
the tubular body and is moveable between a closed seated position
and an open flow through position. In its seated position, the
restrictive element 2 is seated on an annular valve seat 34 which
is carried by the upper edge of the lower body portion 12. The
intermediate portion 21 of the tubular body 1 is provided with at
least one transverse port 27 along its length. In its open flow
through position, the restrictive element 2, in its preferred
embodiment, moves upwardly in the intermediate portion 21, clearing
transverse port 27 and allowing fluid to move upwardly through the
tubular body. A stop shoulder 37 is provided at the upper end of
the intermediate portion 21. The stop shoulder 37 prevents upward
displacement of the valve element 2. The valve seat 34 and stop
shoulder 37 thus define the ends of a chamber 35 in which the valve
element 2 moves.
In order to guide the valve element, in its preferred form, as it
moves between the open and closed positions, the narrow latching
neck portion is formed having both an internal and external
diameter substantially smaller than the corresponding internal and
external diameter of the intermediate portion.
THE VALVE ELEMENT
In its preferred form, the valve element 2 as seen in FIGS. 2 and
3, is a hollow plunger 28 having a second longitudinal bore 38. The
plunger is sized for fitting relationship into the chamber 35 of
the upper body portion 11. The plunger 28 has a lower plunger head
29 and an upper tubular guide shaft 30. The plunger head 29 is
sized to fit loosely within the intermediate portion 21 while the
guide shaft 30 is sized to fit loosely within the latching neck
portion 25. The guide shaft 30 has at least one equalization window
32 formed along its length.
A transverse pierceable disc or wall 31 is formed across the lower
end of the plunger 28, preferably intermediate the guide shaft 30
and the plunger head 29. In this manner, a fluid pocket 33 is
formed beneath the pierceable disc 31 within the confines of the
plunger head 29. As fluid is moving upwardly through the tubular
body 1, the fluid in this fluid pocket 33 remains dead, thereby
decreasing the wear on the pierceable disc. The cross-sectional
area of the pierceable disc 31 is substantially less than the
cross-sectional area of the first bore 36. By this provision, the
disc 31, when pierced, permits a slow rate of flow therethrough to
prevent damage to the submersible pump.
The plunger 28 is preferably machined as a single unit. In this
way, the pierceable disc, being integral with the plunger, provides
the increased strength necessary to support a column of fluid in
the tubing string when the restrictive element 2 is in the seated
position.
By providing a loose fit between the plunger 28 and the chamber 35
of the upper body portion 11, a clearance is provided therebetween.
This clearance is sized to allow sand and shale particles to pass
through the tubular body 1 without lodging therein or causing
abrasive damage to either the tubular body 1 or the plunger 28.
Conceivably, the valve element could take the form of a hinged flap
having a pierceable portion located therein.
OPERATION
The two piece tubular body 1, loaded with the valve element 2, the
packing ring 13 and the ring seat 34, is threaded together. The
body 1, thus assembled, is lowered into well tubing string 4 on a
conventional wireline tool (not shown) which engages latching head
26. Upon reaching the restricted diameter of the seating nipple 3,
the resilient flanges 20 are forced to bend inwardly to clear the
seating nipple 3, springing outwardly again once the restriction is
cleared. Once seated, the tubular body 1 cannot be displaced under
the normal pressures of fluid flow.
To retrieve the tubular body 1, a conventional pulling tool (not
shown) is latched onto latching head 26. An upward force from the
surface is applied to dislodge the device.
As the submersible pump forces the fluids upwardly, fluid pressure
bearing from below against the pierceable disc 31 force the hollow
plunger 28 to move upwardly. This movement clears transverse port
27 to permit the fluid to communicate upwardly past the tubular
body 1 to the surface. In this open flow through position, the
plunger head 29 bears against the stop shoulder 37, thereby
restricting the upward displacement of the plunger 28.
In the event that the pump is stopped, the downward pressure
exerted on the pierceable disc by the column of fluids suspended
above the device forces the plunger 28 to move to a closed seated
position. The plunger is thereby seated on ring seat 34 to prevent
an uncontrolled back flow through the device.
To equalize the pressures above and below the device, a spear (not
shown) is run down the tubing string 4 on a wireline (not shown) to
rupture the pierceable disc 31. The orifice thus formed in the disc
31 is sufficiently small so as to allow the column of fluid above
the device to drain at speeds which do not damage the pump.
Once the pressures have been equalized the device may be retrieved
with a pulling tool (not shown). The plunger 28 and packing ring 13
may be replaced and the device may be rerun back down the well.
The thickness of the disc 31 together with the number of packing
rings 13 and ring seats 34 needed to seal the device against the
pressures of operation are adjusted with the depth of the well.
* * * * *